Enhanced spin polarization of conduction electrons in Ni explained by comparison with Cu

Abstract

The spin-split Fermi level crossings of the conduction band in Ni are mapped out by high-resolution photoemission and compared to the equivalent crossing in Cu. The area of the quasiparticle peak decreases rapidly below Ef in Ni, but not in Cu. Majority spins have larger spectral weight at Ef than minority spins, thereby enhancing the spin-polarization beyond that expected from the density of states. A large part of the effect can be traced to a rapid variation of the matrix element with k at the point where the s,p-band begins to hybridize with the dz 2 state. However, it is quite possible that the intensity drop in Ni is reinforced by a transfer of spectral weight from single-particle to many-electron excitations. The results suggest that the matrix element should be considered for explaining the enhanced spin polarization observed for Ni in spin-polarized tunneling.

Correlation effects in magnetic materials: An ab initio investigation on electronic structure and spectroscopy

“…Also the LSDA + DMFT scheme is able to reproduce the 6 eV satellite structure in the valence band region. As was shown by earlier calculations [25] and was confirmed by photoemission experiments [59], the 6 eV satellite is spin-polarized. In a recent experimental study the XPS intensity at h =150 eV as well as the spin-and angle-resolved photoemission spectra have been measured at h =66 eV [75].…”

“…The electronic structure of fcc Ni has been subject of numerous experimental [55][56][57][58][59][60][61][62] and theoretical studies [63][64][65] as a prototype of an itinerant electron ferromagnet, since shortcomings of simple one-electron theory are obvious. Valence band photoemission spectra of Ni [66][67][68] show a reduced 3d-band width compared to LSDA calculations [69].…”

Electronic structure calculations with dynamical mean-field theory

“…Nickel is more itinerant than iron ͑the spin-spin autocorrelation decays faster͒, which has longer lived spin fluctuations. On the other hand, the one-particle density of states of iron closely resembles the LSDA density of states while the DOS of nickel, below T c , has additional features which are not present in the LSDA spectra ͑Iwan et al Eberhardt and Plummer, 1980;Altmann et al, 2000͒: the presence of the 6-eV satellite, the 30% narrowing of the occupied part of d band, and the 50% decrease of exchange splittings compared to the LDA results. Note that the satellite in Ni has more spin-up contributions in agreement with photoemission spectra ͑Altmann et al, 2000͒.…”

Magnetic properties of ultrathin3dtransition-metal binary alloys. I. Spin and orbital moments, anisotropy, and confirmation of Slater-Pauling behavior

“…5. It is understood that the s-p bands are strongly hybridized with the d band near the Fermi surface, giving rise to a high degree of spin polarization for the conduction bands in Ni near the Fermi surface, as revealed by angle resolved photoemission spectroscopy (ARPES) [49]. On the other hand, the d bands in Fe are believed to be more localized [5,50,51].These considerations side with the value of the x intercept of the linear fit to the data, which is close to M S of Ni.…”